1. Field of the Invention
This disclosure relates to wireless communication systems, and in particular to a wireless communication system including antenna arrays at both the transmitter and receiver for very high data rate communication.
2. Description of the Related Art
The use of wireless transmission techniques for data and voice communications within closed environments, for example, office buildings, frees users from the necessity of installing cables, bridges, routers, hubs, etc. which interconnect the various data and voice communication equipment. In addition, the elimination of interconnecting cables increases the flexibility of the equipment by facilitating changes in existing equipment configurations, as well as the addition of new equipment without the costly rewiring expenses. However, indoor wireless communications at very high data rates, for example, rates in excess of 10 Megabit per second (Mbps) up to multi-Gigabit per second (Gbps), present technical obstacles affecting the signal integrity. Specifically, signal power margin may be reduced and multipath delay spread may be present.
Wireless communication systems have been developed implementing various transmission techniques to achieve indoor wireless communications at high data rates on the order of Mbps. For example, cordless radio telephone systems have been implemented which permit telephones to communicate via radio to a localized antenna connected to a base station. Infrared communication systems for transmitting two way data communications in the infrared spectrum have also been developed.
More recently, a wireless system for wideband indoor communications using radio as the transmission medium is presented in U.S. Pat. No. 4,789,983 to Acampora et al. The communication system described therein includes a plurality of transceivers associated with separate users of the system, and a central node capable of providing duplex communications using a wireline connection and a radio channel with certain subgroups of transceivers.
Other wireless systems are presented in T. A. Freeburg, “Enabling Technologies for Wireless In-Building Network Communications—Four Technical Challenges, Four Solutions”, IEEE COMMUNICATIONS MAGAZINE, April 1991, pp. 58-64. In T. A. Freeburg, supra at p. 63, a system using six equal 60° azimuth directional antennas with a single elevational beamwidth coverage to operate at 15 Mbps for both transmit and receive. Such a large beamwidth of 60° azimuth and a single elevational beamwidth coverage are used to achieve a required gain.
Such indoor communications techniques do not overcome the signal power margin and multipath delay spread phenomena encountered at data rates of tens of Mbps to data rates in excess of 1 Gbps.